The present invention relates to abnormality diagnosing method and apparatus for sound or vibration that allow the presence or absence of abnormality in a plurality of sound sources or vibration sources to be diagnosed on the basis of an analysis result of sound or vibration at a single evaluation point.
To find at an early stage various kinds of abnormality generated in a sound source or vibration source located in a space is an important issue in various fields of industry. For example, in an automobile having a large number of sound sources or vibration sources, when a failure occurring in each sound source or vibration source is found at a not-yet-serious stage, an appropriate countermeasure needs to be taken for the failure part, this avoids transition to a serious failure or occurrence of an accident caused by the serious failure. This provides usefulness in the improvement of safety.
When abnormality occurs in a sound source or vibration source, in general, sound or vibration varies in the generation part. Thus, when detecting means for sound or vibration is provided in each sound source or vibration source while the detection result of the detecting means is analyzed, abnormality can be found at an early stage. Nevertheless, in the case of an automobile described above, a large number of sound sources and vibration sources are present. Thus, it is not practical to provide detecting means individually in all these sources.
On the other hand, a large number of analysis methods for sound or vibration for identifying a sound source or vibration source have been proposed in the prior art. A widely adopted analysis method is a method based on the FFT (Fast Fourier Transform). In this method, a detection result of sound or vibration acquired as a waveform signal is processed by Fourier transformation, so that spectral intensity is obtained for each frequency component. Each of a detection signal of sound or vibration at an evaluation point set up in a target space and detection signals of sound or vibration at a plurality of candidate points expected to be a sound source or vibration source is processed by Fourier transformation. Then, the spectrum distribution at each candidate point is compared with the spectrum distribution at the evaluation point, so that a sound source or vibration source is identified.
Further, as for analysis methods for sound or vibration employing time information, an analysis method is based on the wavelet analysis. An abnormality diagnosing apparatus employing this method is proposed in the prior art (see, for example, Japanese Patent Publication No. 3561151). This abnormality diagnosing apparatus detects a waveform signal generated in a target object, then performs wavelet transformation, and thereby performs abnormality diagnosis of the target object on the basis of the result of the transformation. More specifically, this abnormality diagnosing apparatus is provided with analysis function determining means that automatically derives a mother wavelet appropriate for the abnormality diagnosis of the target object on the basis of the input waveform signal. Then, on the basis of the mother wavelet derived by the analysis function determining means, the abnormality diagnosing apparatus performs wavelet transformation on the waveform signal detected by a sensor, and then performs abnormality diagnosis of the target object on the basis of the transformation result. The analysis function determining means performs Fourier transformation on a plurality of waveform signals detected by the sensor, then performs inverse Fourier transformation on the average Fourier data obtained by averaging the Fourier transformation results, and thereby derives a mother wavelet.